Congenital facial paralysis refers to
conditions that are acquired during or at birth
(e.g. from trauma), while developmental facial
paralysis (DFP) is the result of developmental
mishaps during fetal development. DFP can
present in isolation or as part of a recognised
syndrome, such as Moëbius, Goldenhar,
etc.

In general, DFP carries a poor functional
prognosis and the importance of early
recognition and treatment has been stressed by
many authors, while most traumatic cases are
likely to recover spontaneously.

Anatomy

The facial nerve arises from the brain stem
nuclei. The motor fibers of the facial nerve
loop dorsally around the abducens nerve nucleus
and exit at the cerebellopontine angle. The
parasympathetic and sensory fibers form the
nervus intermedius which join the motor root of
the facial nerve as it exits the brainstem.

The course of the facial nerve is divided
into the cisternal segment in the
cerebellopontine angle, the intracanalicular
segment, the labyrinthine segment and the
tympanic segment (separated by the anterior
genu), the mastoid segment (separated by the
posterior genu), and the extracranial
segment.Several branches are given off during
the intrapetrosal course. The extracranial
segment consists mainly of the parotid portion
of the facial nerve and its terminal branches
that innervate the facial musculature.

Embryology

The facial nerve begins to develop at 3
weeks of life from the facio-acoustic primordium
and is intimately related to the structures of
the middle ear, external ear, parotid gland, and
facial muscles. The neural connections are
completely established by the 16th week of fetal
life, while the facial nerve separates from the
acoustic nerve at 5-6 weeks of fetal life.
Therefore, an in utero insult prior to this
time, can affect both nerves. The facial canal
continues to develop after the 16th week and the
ossification is completed by the end of the
first year of life. The inner ear and internal
auditory canal undergo a different
embryogenesis.

Although causes of DFP have been attributed
to an agenesis of the petrous portion of the
temporal bone, with resulting agenesis of the
facial nerve, it should be pointed out, that the
bone and cartilage formation occur after the
development of the facial nerve and thus appear
unable to influence the nerve itself.

At birth, the anatomy of the facial nerve
approximates that of the adult with the
exception of the nerve's exit through the
superficially located stylomastoid foramen,
making the facial nerve vulnerable to
compression injury from the shoulder during
intrauterine life, the maternal pelvis in labor,
or the forceps during delivery. The mastoid tip
develops postnatally which affords greater
protection to the nerve in later life.

Moëbius'syndrome

Moëbius syndrome, or better
Moëbius sequence, is a non-progressive
congenital condition with an estimated
prevalence of 0.0002- 0.002% of births.In most
studies, Moëbius sequence has been defined
as a congenital facial weakness with congenital
impairment of ocular abduction.

Moëbius'syndrome represents a broad
spectrum of clinical findings ranging from
isolated unilateral facial paralysis to
bilateral absence of facial and abducens nerve
function. Multiple other cranial nerves,
including the glossopharyngeal, vagus,
hypoglossal, and other extraocular motor nerves,
can be affected.

The complete pathophysiological description
of Möbius syndrome remains elusive. Whether
nerve, brainstem, or muscle aplasia is the
primary event has not been established. Genetic
factors, teratogens and vascular anomalies have
been linked with the aetiopathogenesis of the
syndrome.

Because of the early age at which the
syndrome becomes apparent, affected individuals
generally are brought to medical attention by
their parents or other caretakers as
infants.

Facial and ocular symptoms are usually the
presenting problems:

Facial diplegia is the most noticeable
symptom. This may be observed soon after birth
with incomplete eyelid closure during sleep,
drooling, and difficulty sucking.

On occasion, the facial paralysis is not
noticed for a few weeks or months until the
inability to smile, to yawn or the lack of
facial movement with crying arouses the parents'
concern.

Because of the facial and forehead
immobility, the skin appears devoid of wrinkles.
Inability to close the mouth is the rule.

Speech is usually indistinct secondary to
the inability to close the lips and make labial
sounds. While eating, food is apt to lodge in
the cheeks.

Intelligence is usually normal, but mild
mental retardation is thought to occur in about
10% of cases. The intelligence may be
underestimated without formal testing because of
the facial appearance.

I submitted a survey on 2012 April 2. I have
left some blanks so I hope to explain them here.
Our son was adopted last year from Bulgaria at
the age of 7. He had not been diagnosed with
Moëbius Syndrome while in the orphanage.
That diagnosis was made after we had him home
for several months. We
have never seen him yawn. We don't
know if his mother had an ultrasound during her
pregnancy. He does wake during the night about
once or twice a week but it is still too soon to
tell what the cause of it is. There are so many
things that can be a factor after growing up in
an orphanage for 7 years.

Thank you for your research. I hope to
learn more of
the connection between Moebius and yawning.